The present invention relates to electronic devices, and, more particularly, to semiconductor devices useful in telecommunications.
A trend in equipment maintenance is to remote maintenance via telephone lines. Teleserviced equipment can be monitored around the clock in order to pinpoint problems before machinery breaks down. Anomalies may be automatically called in to a service center, and with the aid of diagnostic programs and a history file intelligent troubleshooting may be performed via the global telephone network. For example, consider the servicing problem encountered by manufacturers of factory robots. When a robot malfunctions, a whole assembly line can go down, and the robot manufacturer typically must quickly dispatch a highly trained technician to a site in another city with no guarantee of when the problem will be isolated and fixed. Not only does this incur travel costs; it also wastes the time and money of the robot user as his assembly line remains idle. But with teleservicing the robot can be interrogated remotely using a modem connection and a service manager computer. By running remote diagnostics over the dial-up telephone network, the robot's problem might be quickly identified and repaired without the need for human intervention. Perhaps the robot's software was an early revision with subsequently discovered bug; in such a case teleservicing enables instant, automated reloading of a new software version in the remote robot. In addition teleservicing can perform preventive maintenance: equipment can be automatically monitored and queried at times of low telephone use to verify correct operation.
Teleservicing can also mean the automated retrieval of information over the telephone. For example, an automated literature distribution system could use digitized high-fidelity speech to guide a human caller through a DTMF-controlled menu for selection of graphics information to be later transmitted to the caller's FAX machine. Such an application would require DTMF detection, digital speech playback, modem data transmission, and FCC-approved telephone line interfacing.
A problem of teleservicing is the number of telephone lines needed for a system with many remote sites to monitor and service. The present invention provides for detection of loop current changes in the telephone line. Such a detector may be incorporated into remote equipment; and this would permit the equipment to unobtrusively use already existing telephone lines. That is, if a remote piece of equipment is transmitting or receiving information on a telephone line and if someone picks up a telephone handset to make a call on the same telephone line, then the loop current drops and the piece of equipment can terminate its transmission and signal its host to also terminate transmission within a fraction of a second and without any apparent impact of the person attempting to make a call. In this manner multiple pieces of equipment can share a telephone line with a priority user and be teleserviced without any influence on the priority user's access to the telephone line. Preferred embodiments include a loop current detector that digitally stores sampled loop current, and thus makes the value available for use or monitoring by a teleservicing host.